Purification of cellulose ethers



Patented I Sept. 14, 1926.

UNITED STATES ATENT OFFICE.

JEAN ALTWEGG AND CHARLES ANTOINE MAILLARD, F LYON, FRANCE, ASSIGNORS TO SOGIETE CHIMIQUE DES USINES DU RHONE, OF PARIS, FRANCE.

' runmrcarrolv or GELL'ULOSE nrnnns. I

No Drawing; Application filed. october 20, 1925, Serial No. 63,758, and in France December 22, 1924. i

The cellulose ethers produced by known methods, by means of industrial apparatus have usually been obtained in the form of masses more or less coloured. The solutions I of these crude ethers in the suitable solvents exhibitthe same colorations, as well as varnishes, films, filaments, etc. obtained with these ethers'as crude materials.

It is therefore necessary to submit .the

crude ethers to a purifying and a bleach-v ing treatment, so as to 'render them suitable for use in the manufacture of colourless varnishes and objects of various nature.

It ethers have already been proposed- In most methods, the ether is dissolved in a suitable solvent and is re-precipitated by a liquid which is mixable with the solvent but which is not a solvent of the ether to be purified. In this manner it is possible to somewhat attenuate the initial colour of the crude ether, but absolute colourlessness is not reached, however, even when these operations are repeated a large number of times. ,A. portion of the impurities is always retained by the principal ether.

It-has also been proposed to wash the ethers, when in the solid state, with dilute acids, particularly with dilute nitric acid. The latter process does not, however, yield .colourless ether, any more than the former. The purification method, object of the present invention is based on the action 9f. strong acids upon the crude ethers in solution, as revealed by the observation that a solution of crude ethers in a suitable solvent becomes gradually colourless afterthe addition-6f a certain quantity of, strong acid.

By precipitation, a white purified'ether is obtained which, when re-dissolved, g'ives colourless solutions. As solvent liquid, acetic acid or any other suitable solvent, or mixtures of solvents, may be used. The strong acids which, may be usedv for this urification are numerous. e mentioned sulphuric and hydrochloric acigs, then nitric and phosphoric and other ac1 s. 1

In carrying out this new process in practice a definite quantity of strong acld is added to the solution of cnu'defether, and allowing it to react for a certain length ""of time, the ether is Ire-precipitated by means'of a non-solvent liquid.

65 The quantity-of strong acid to be em Foremost can tion of the action of the acid, which duration may vary from a few minutes to several hours.

Generally the'operation can be performed quite satisfactorily at ordinary temperature, but heat may be applied, provided that the rea'ction temperature selected is not such as p to be a source'of danger. Several methods of purification of crude lose ether is obtained, by precipitation'in a. large quantity of water, under the form of a whlte mass which, washed-and dried,'constitutes a valuable raw material for the manufacture of varnishes, collodions, celluloids, films, threads, or fabrics.

Example I I .,50 parts of crude ethyl cellulose containing about 40% of ethoxyl groups are dissolved in 500 parts of alcohol at 93, and 15 parts of sulphuric acid 35 B. are added with'jstirring. Afterstanding for one hour at a temperature of 20 to 25 C; the mixture is poured in water and filtered, and the purified ether is washed and dried. 4 Ewample Ill.-By replacing in Example 'I the crude-ethyl-cellulose by a crude methyl-cellulose obtained by the action of the methyl sulphate on sodium cellulose, a methylic ether of great purity is obtained.

What we claim and desire to secure by Letters Patent is 1. A process of purification of cellulose ethers consisting in causing a small quantity of a-strong acid to react on asolution of the crude cellulose ether and in precipitatingby a liquid mixable with the solvent,

but not being a solvent of the ether to be 2.1A process of purification of cellulose ethers consisting in causing a small quantity cellulose, which consists in forming an alcoof hydrochloric acid to react on a solution holic solution of the cellulose ether and/addof the crude cellulose ether, and in precipiin thereto hydrochloric acid, the acid and 15 tating by a liquid mixable with the solvent, so ution being in the approximate propor- 5 but not being a solvent of the ether to be tions by weight of one and forty respecpurified. tively, stirring the mixture and re-precipi- 3. A rocess ,of purification of crude tating with water. ethyl-eel ulose consisting in forming an In testimony whereof we have signed ou 30 alcoholic solution of the cellulose ether, addnames to this specification. l0 ing hydrochloric acid with stirring and reprecipitating with water. JEAN ALTWEGG.

4. The process of purifying crude ethyl- CHARLES ANTOINE MAILLAR/D. 

